Error OpenTopoMap

Since yesterady night I do not get the OpenTopoMap loaded. ALso https://opentopomap.org was offline for hours. Meanwhile https://opentopomap.org is back again, but my OpenTopoMap does not load. I use:

Standard
https://{s}.tile.opentopomap.org/{z}/{x}/{y}.png

Alternative
http://opentopomap.org/tiles/${z}/${x}/${y}.png
http://a.tile.opentopomap.org/${z}/${x}/${y}.png
http://b.tile.opentopomap.org/${z}/${x}/${y}.png
http://c.tile.opentopomap.org/${z}/${x}/${y}.png

Anyone else having issues with OpenTopoMap? I can’t find anything online about an issue they have.
If it’s working for someone, please tell me your tiles URL

Thanks
Sven